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Abstract

We report on a new technique for entanglement distillation of the bipartite continuous variable state of spatially correlated photons generated in the spontaneous parametric down-conversion process (SPDC), where tunable non-Gaussian operations are implemented and the post-processed entanglement is certified in real-time using a single-photon sensitive electron multiplying CCD (EMCCD) camera. The local operations are performed using non-Gaussian filters modulated into a programmable spatial light modulator and, by using the EMCCD camera for actively recording the probability distributions of the twin-photons, one has fine control of the Schmidt number of the distilled state. We show that even simple non-Gaussian filters can be finely tuned to a ∼67% net gain of the initial entanglement generated in the SPDC process.

Figures (6)

Fig. 2 Images recorded with the EMCCD camera for computing the initial Schmidt number K0. In (a) we show the near-field distribution generated by the transverse pump beam. In (b) we show the far-field distribution that arise from the phase-matching conditions. (c) and (d) show the corresponding fitting surfaces.

Fig. 3 Numerical simulations for our entanglement distillation protocol. (a) The ratio K/K0 of the post-selected states when a and d are varying. (b) The success probability Psucc as function of a and d.

Fig. 4 Some examples of the experimental results obtained for the first scenario considered, where d is fixed to 20 px and a is varying. In (a), (c) and (e) we show the recorded images at the near-field plane when a = 6, 8 and 14 px, respectively. (b), (d) and (f) show the corresponding recorded images at the far-field plane when a = 6, 8 and 14 px, respectively.

Fig. 5 Some experimental results obtained for the second scenario considered, where d is varying. In (a), (c) and (e) we show the recorded images at the near-field plane when d =0, 14 and 19 px, respectively. In (b), (d) and (f) we show the corresponding recorded images at the far-field plane when d = 0, 14 and 19 px, respectively.

Fig. 6 Experimental results for both scenarios considered for the entanglement distillation procedure. In (a) we show the recorded K values when d is fixed at 20 px while a is varying. In (b) we show the obtained K values when a is fixed at 7px and d is varying. Black dots correspond to the experimental results and the blue dashed line shows the initial value of the spatial entanglement K0. The pink area represents the confidence bound of K obtained by Monte-Carlo simulations and based on the experimental errors.